Safety

Studies done in the U.S., Europe, and Australia have found that roundabouts have better safety performance over types of intersections. Surveys have also shown that the damage incurred in roundabout crashes was significantly reduced. The Insurance Institute for Highway Safety published A Study of Crash Reductions Following Installation of Roundabouts in the United States, in May 2000, illustrating the reductions of crashes after the introduction of a roundabout.

Lower absolute speeds. Allowing more time for drivers to react while reducing crash severity

Pedestrians only have to cross one direction of traffic at a time

One-way operation. Vehicles travel in the same direction virtually eliminating the possibility right angle or head-on collision

Parking isn’t permitted within the roundabout

Environment

The nature and design of roundabouts can provide environmental benefits. As the vehicle delay, number and duration of the stoppages are decreased compared an alternative intersection, roundabouts may:

Reduce air quality impacts

Reduce noise

Reduce fuel consumption

Cost

Maintenance costs for signalized intersections can vary depending on the size of the intersection; however, over a life cycle of an intersection regular costs include electricity, repairs of loops, controller, signal heads (which need to be replaced and completely rebuilt on a regular basis), and timing plans. Maintenance costs for modern roundabouts are limited to landscape maintenance of storage area (if landscaped) and sign replacement (as needed).

Construction costs for roundabouts can vary depending on size. Roundabouts can cost as much or more than a large signalized intersection. Comparatively, the lifetime maintenance costs of a roundabout versus a signalized intersection show that there is a higher benefit to cost ratio for the roundabout. The 25 year lifecycle of a roundabout ultimately offsets the construction cost when compared to a 10 year lifecycle of a signalized intersection.

Factoids

Griffith and Albany, Australia, have no traffic lights, only roundabouts

Swindon, England’s “Magic Roundabout” contains 5 mini-roundabouts

The BBC list’s New York’s Columbus Circle as the first

The London IMAX cinema was build in the center of a roundabout

The first (pre-modern) roundabout entered service in 1907 in Paris around the Arc de Triumphe

The first modern roundabouts were built in 1966 in the United Kingdom

Las Vegas has the first modern roundabouts built in United States (built in 1990)

The largest modern roundabout in the United States is in Clearwater, Florida